Method of making embedded bars



Nov. 22, 1938.

B. F. FRIBERG METHOD OF MAKING EMBEDDED BARS Filed May 17, 1955 v I. x M

FIGJ.

INVENTOR B.F.FR|BERG A TRNEY Patented Nov. 22, 1938 UNITED STATES METHODOF MAKING EMBEDDED BARS Bengt F. Friberg, St. Louis, Mo., assignor toLaclede Steel Company, St. Louis, Mo., a corporation of MissouriApplication May 17, 1935, Serial No. 22,001

1 Claim.

Bars embedded in concrete structures require bonding means in additionto the cohesion between the concrete and the surface of the bars inorder that the required stresses may be carried by the bars withoutcausing rupture between the bars and the cement. Particularly is thistrue at the ends of the bars where the bond stresses are greatest, or atintermediate points of the bars where abrupt change in location of thebars or sudden changes in the forces acting on the structure cause rapidchange in the stresses carried by the bars.

Among means heretofore employed to secure anchoring of the bars at theirends are the following:

The ends of the bars have been provided with semicircular hooks. Theends of the bars have been upset with or without threading of the upsetportion. The ends of the bars have been provided with plate structurepositioned within or just outside of the concrete and secured to thebars by welding or by a threaded connection. All these means can beutilized only at the ends of the bars and necessarily extend for aconsiderable distance at one side of or around the bars, thus creating acrowded condition not conducive to the best results in pouring concreteand carrying the stresses. Such stresses may, therefore, be highlyconcentrated and improperly distributed, producing a tendency to splitor crush the material in which the bars are embedded.

The bond strengthening means commonly used in an intermediate portion ofa bar consists in providing the bar with deformations or protrusionsformed in the operation of rolling the bar. These protrusions, due totheir method of formation, can only be of relatively small size and mustbe distributed uniformly along the bar, They are, therefore,insufilcient to provide the necessary bond between the bar and theconcrete at the points of greatest stress.

The object of my invention is to provide a form of bond strengtheningmeans for bars enclosed in cementitious material which may be applied atany point or points along the bar and which may be made of any desiredsize and so distributed around and along the bar as to avoidconcentration of stresses between the bar and the concrete which areliable to cause localized crushing of the concrete, and also to avoidany eccentric location of the anchoring and bond strengthening means.

In the accompanying drawing, which illus trates some applications of myreinforcing bar anchorage, Figure 1 is a vertical section through a beamstructure; Figure 2 is a section taken on the line 2 2 of Figure 1;Figure 3 is a vertical section through another form of beam in which thebar consists of a hanger rod having short embedment; Figure 4 shows theanchorage applied to an embedded bolt; Figure 5 is an enlarged side viewof a deformed bar embodying my invention; and Figure 6 is a sectiontaken on the line 6-6 of Figure 5.

In carrying out my invention I utilize any 10 usual form of reinforcingbar having round, square, or other cross-section, and either plain ordeformed. In Figure 5 I have shown in detail a deformed bar It] to whicha spiral anchorage H is applied. The anchorage is formed of a spiralwire. This spiral may be pro-formed, compressed to increase its internaldiameter, passed over the bar, and allowed to expand into firm contacttherewith, or it may be wound directly upon the rod. Either at the timeof or an after application, the coil is welded to the rod so as to formsubstantially an integral structure therewith It will be evident thatthe wire size, the number of turns, and pitch, i. e., the distancebetween successive turns, may be chosen so that the maximum bondstrengthening effect is obtained exactly where desirable and withoutliability of crushing or splitting the concrete.

In Figures 1 and 2 I have shown a structure including an upright l2 anda beam l3 in which structure are embedded in the bottom of the beam tworound reinforcing bars I4 and one square reinforcing bar I5 bent up intothe top of the beam over the support. The ends of the bars at thesupporting element I 2 where the maximum bond stresses occur in thestructure illustrated are provided with spiral anchorages H.

In Figure 3 I have shown a beam and slab structure l6 which is wholly orpartially supported by a suspension rod l1 having the spiral anchorageII applied to substantially the entire portion of the bar embedded inthe concrete.

In Figure 4 I have shown a structure in which the bar is in the form ofa bolt I8 applied to a block 19 of concrete, stone, or masonry. In thisconstruction a hole 20 is drilled in the block, which hole is of thesame or but slightly greater diameter than the external diameter of theanchoring coil I I carried on the bolt. Grouting 50 2| fills the spacearound the bolt. The grouting may be firmly packed in the opening byrotating the bolt, the spiral l l acting as a screw propeller to performthe packing operation,

While I have shown the spiral anchorages as 55 claim as new and desireto secure by Letters Patent of the United States is:

The method of providing a bar with anchoring means which comprisespre-forming a coil, compressing the coil, applying it to the bar,allowing 5 it to expand into intimate contact therewith, and welding itthereto to form a substantially integral part thereof.

BENGT F. FRIBERG.

